Lecture 2 Flashcards
receptors
stimulus energy to electric potentials can be transmitted and interpreted by the nervous system
sensory neuron
pns pathway to cns
mechanoreceptors-
photoreceptors-
chemoreceptors-
thermoreceptors -
mechanical energy
light nergy
chemical energy
thermal energy
common to all sensory receptors
mechanisms by wich the stimulus energy leads to change in the electrochemicla state of the cell or axon
a mechanism to convert passive receptor potientials into an action potential
how are receptor potentionals generated
gerenarated by the influx and efflux of ions
how are action potentioan generated
generated by the influx efflux of ions and are kept alive bc they regenerate
types of stimulus segregation by receoptors
- type
- duration, onnset, offset
- intensity
- location
Stimulus modality stuff
somatosensory
vestibular
visual
auditory
somatosensory
any mechanoreceptors or themoreceptros or nociceptors that are in skin, fatty tisue beneath the skin, muscle or muscle tissue
Vestibular
mechanoreceptors in the otoliths/labrynths of the inner ear
Visual
photoreceptors located in the retina
auditory
mechanoreceptors located in the cochlea of the ear.
fast adapting and slow adapting sensory responces
Fast adapting is vigorous but transient. responds to sudden changes in the stimulus energy
Slow addapting is measured but sustained and responds to a constant stimulus energy.
how does photoreceptors work
absorb photons from visible light wavelenghths leading to a chemical reaction that generates the receptro potential
pathway for photo receptors when light hits them
pigment absorbs light
Na+ gated ion chanels are cloosed
this decreases the receptor potential
this releases less nuerotransitters
how does photoreceptors work with bipolar cells
they use bipolar cells to sned a clear stimulus to the ganglia wich is the sensory nerve. The smaller the receptor potential the stronger the stimulus energy
the two types of photoreceptors
how much they represent
where they located
what they have
what colours they do
rods and conses
96 % rods 4% cones
Rods: along the border of the retina
Cones: in the middle of the retina
Rods: have rhodhopsin
Cones: have iodopsin
Rods: cyan/green
cones: there are three types each representing thier own waveleghnths
what are hair cells and what do they mediate
mechanorepceptors that mediate audio and vestibular senses
embedded in the semicircular canals mediate out sense of angular head rotation
The tonotopic map
generated by the differential composition of the basilar membrane as it winds around the cochlea
The locations of the specific axons generating action potentials represents a specific frequency of sound
Semi circuluar canals that mediate sense of angular head rotation
Horizantal canal - Head yaw (head side to side)
Superior canal - Head pitch (nodding of the head)
Posterior canal - Head roll (moving the head to touch shoulder)
Hair cells embedded in the otolith organs (mechanoreceptors: hair cells)
Hair cells embedded in the otolith organs mediate our perception of head translation and gravitational forces
Otolith organs: Utricle (Hair cells)
responsible for horizantal acceleration of the head
Otolith organs: Saccule (Hair cells)
responsible for the vertical acceleration of the head (relative to gravity)
Mechanoreceptors: Cutaneous receptors
translate mechanical forces acting on the skin into receptor potential through mechanically gated ion channels
What are the cutaneous mechanoreceptors
Meissner’s corpuscles
Pacinian corpuscle
Merkel disk receptor
Ruffini ending (SA)
Cutaneous mechanoreceptors : corpuscles
Na+ and Ca2+ ions channels on an exposed nerve ending are mechanically deformed as corpuscle is compressed
Merkel disk and Ruffini endings
Na+ and Ca2+ ions channels on an exposed nerve ending are mechanically deformed as skin is stretched
Mechanical deformation creates a pore for ions to flow through
What are the superficial cutanous receptors (1)
Messner corpuscles (RA1)
Merkel disk (SA1)
what are the fast adapting cutaneous receptors (RA)
Meissner corpuscles (RA 1)
Pacinian corpuscle (RA 2)
What are the deep cutaneous receptors (2)
Pacinian corpuscle (RA2)
Ruffini ending (SA2)
What are the slow adapting (SA)
Merkel disk (SA1)
Ruffini ending (SA2)
Superficial cutaneous receptors
Have small receptive fields
Are densely populated in areas of the skin used to explore objects
Deep receptors
Have larger receptive fields
Are best situated to detect vibrations in objects (shifting liquid inside a water bottle)k
Mechanoreceptors: Proprioceptors
Proprioceptors translate mechanical forces generated by the body’s own position and movement
Internal sense of body
Proprioceptors: Golgi tendon organ
Tuned to sense muscle force
Proprioceptors: muscle spindle fibers
Tuned to sense muscle length (sensitive to stretch)
Proprioreceptors: Joint receptors
Tuned to sense (extreme) joint angles
Protective against injury
Orientation of spindle fibers (proprioceptors)
Spindle fibers (intradusal muscle fibers) are positioned parallel to standard skeletal muscles fibers (extrafusal muscle fibers)
Lengthen and shorten as extrafusal fibers contract and relax
What happens when muscle relaxation stretches the spindle fibers (proprioceptors)
tension on the spindle fiber surface pulls open the mechanically gated ion channels
influx of ions generates a receptor potential
What happens when muscle contraction releases stretch tension
mechanically gated ion channels fold in on themselves
Ions channels become less permeable, decreasing the receptor potential
What are the two classes of spindle fibers (proprioceptors)
Dynamic Group
Activity is a function of both muscle length and rate of change in muscle length
Static Group
Activity is a function of muscle length
Where are the Golgi Tendon Organs and how do they work???
located in series between the muscle fibers and the muscle tendon
Forces generated by the mucles and transmitted to the bone (via the tendon) must act on the GTO
Mechanoreceptors: Nociceptive receptors
Nociceptive mechanoreceptors translate mechanical, chemical and thermal forces from damaged tissue or the threat of damage to tissue
bare nerve endings
Nociceptors are senstivie to..
Thermal - activated by extreme temperatures
Mechanical - activated by intense pressure on the skin
Chemical - activated by internal or external toxins
Polymodal - activated by chemical, thermal or mechanical stimuli
